The SFF4393/18 from Solid State Devices is a Junction Field Effect Transistor (JFET) with Drain Saturation Current 5 to 30 mA, Gate Source Voltage -40 to -57 V, Continous Drain Current 50 mA, Drain Source Resistance 100 Ohm, Gate Reverse Current -130 to -200 nA. Tags: Through Hole. More details for SFF4393/18 can be seen below.